Neonatal bacterial infection is a major cause of morbidity and mortality in the United States affecting up to 1% of all newborns and up to 30% of very low birth weight (VLBW) newborns. It is associated with signficantly lengthened hospital stays and has mortality rates ranging from 10-70% depending on the organism involved and the complications present at the time of diagnosis. The high incidence of bacterial infection in VLBW infants is a result of their immunologic immaturity complicated by the use of invasive monitoring and support devices and exposure to a wide range of potential pathogens in the neonatal intensive care environment. The purpose of this Phase II Multicenter study was to: Determine the safety, tolerance to Filgrastim which will be assessed by reference to adverse event profile and laboratory data; and to evaluate if Filgrastim, compared to placebo, in 500-1500 gram neonates with late- onset sepsis results in a decrease in the proportion of patients experiencing treatment failure.